An access point may allocate “a period in which a terminal can transmit a signal without conflicting with other terminals (noncompetition period)” to each terminal (scheduling), and each terminal may be activated in the noncompetition period which is allocated to the corresponding terminal. Further, an access point may allocate a dedicated period for retransmitting traffic of which the delay permission period is equal to or less than a threshold value to each terminal.
However, since “the period in which the terminal can transmit a signal” (communication period) is set in advance by the access point, according to the degree of degradation of the propagation environment, the communication period may expire before each terminal retransmits the signal that the terminal has failed to transmit. In this case, QoS (Quality of Service) requirements may not be satisfied. On the other hand, if it is assumed that the access point dynamically allocates the communication period to each terminal, it is necessary for the terminal to await the signal for being allocated the communication period, and power consumption may not be reduced.